The invention relates to a complex magnetic head and manufacturing method thereof for writing and reading magnetic data on the magnetic recording medium by a plurality of data tracks.
In recent years, the size of floppy disks and floppy disk drives (FDD) are becoming smaller such as 8 inches.fwdarw.5.25 inches.fwdarw.3.5 inches. In more recent years, since the need for the note book type of personal computer is especially increasing, demand for the small FDD of 3.5 inch type is rapidly increasing.
Regarding the capacity of FD (Floppy disk), unformatted 1 MB, 1.6 MB and 2 MB type are widely used. The FDD system for these FD uses a tunnel erase system. The upper rank 4 MB FDD using an advanced erase system is going to be shipped in the FDD market. The computer software is becoming larger in proportion to the progress of the information society, and also the demand is increasing for large capacity of FDD which is larger than that of existing FDD by more than 10 times. In order to realize such large capacity FDD using 3.5 inch size FD, it is necessary to use the servo-tracking technology adopted in the hard disk apparatus for increasing the track density, and also to use high recording density medium (e.g. metal disk) and high recording head (e.g. MIG head) for increasing line recording density. Further, in order to use the existent software effectively, it is necessary to provide compatibility with lower rank FDD. That is, the large capacity FDD has to read and write for 4/2/1.6/1 MB disks which have the same track width. Most of the existing higher rank apparatus has this function for the lower rank apparatus. The complex magnetic head apparatus of the present invention can realize the above mentioned large capacity FDD having compatibility with lower rank FDD.
It is said that FDDs have been popular because they have high compatibility between systems via floppy disk, that is between FDDs. In order to assure data compatibility, the data is recorded in a little narrower track width compared with the track pitch. For example, in the 3.5 inch 4 MB FDD using advanced erase head and having 135 TPI (track number per inch) track density, the track pitch is 188 .mu.m and the data track width is 120 .mu.m (track width of R/W head). The remaining 68 .mu.m is called a guard band, and in that area there is no recorded data and no signals. If there is no position drift (off-track), the guard band is not needed. It is sufficient to provide only a R/W head track width. In order to assure the guard band between the data in the case of the off-track situation, an erase head having 250 .mu.m track width is arranged at some distance before the R/W head. Since the existing low density FDD adopts the above recording system, it is difficult to increase the track density. In order to increase the track density, a closed loop system has been proposed instead of the existing open system using a stepping motor. But the closed loop is very expensive because it uses a track servo apparatus.
FIG. 28 is a perspective view of the prior art complex magnetic head shown in the laid-open patent publication No. 63-103408. In the figure, 1 is a slider. 2 is a first R/W (read write) core assembled in the slider 1. 3 is a first R/W coil coiled around the first R/W core 2. 4 is a first R/W gap formed by the first R/W core 2. 5 is a first R/W head assembled from these elements 2.about.4. 6 is a second R/W core assembled in the slider 1 together with the first R/W core 2. 7 is a second R/W coil wound around the second R/W core 6. 8 is a second R/W gap formed by the second R/W core 6. 9 is a second R/W head assembled from these elements 6.about.8.
10 are first erase cores for erasing both side of the data track on the magnetic disk (not shown in the figure) recorded by the first R/W gap 4. 11 are first erase gaps formed by the first erase cores 10. 12 is a first erase coil wound around the first erase cores 10. 13 is a first erase head assembled by the elements 10.about.12. 14 are second erase cores for erasing both side of the data track on the magnetic disk (not shown in the figure) recorded by the second R/W gap 8. 15 are second erase gaps formed by the second erase cores 14. 16 is a second erase coil wound around the second erase core 14. 17 is a second erase head assembled by the elements 14.about.16.
The track width of the R/W cores 2 is formed wider than that of the R/W track 6. A first complex head assembled from the first R/W head 5 and the first erase head 13, and a second complex head assembled from the second R/W head 9 and the second erase head 17, are separately formed. then the two complex heads are assembled into one slider 1. The complex head with narrower track width is called a higher rank complex magnetic head, and the complex head with wider track width is called a lower rank complex magnetic head.
The operation of the above conventional complex magnetic head is explained here. Generally, the magnetic head operates as an electro-magnetic transducer or magneto-electric transducer when the magnetic head reads or writes the information on the magnetic disk. In the case of writing information on the data track on the low density magnetic disk, the signal current flows in the first R/W coil 3 of the lower rank complex magnetic head having wider track width. In response to the signal current flowing the first R/W coil 3, a strong magnetic field is generated around the first R/W gap 4 and the information is written in the magnetic recording medium on the surface of the magnetic disk.
The magnetic head reads the information on the data track by amplifying voltage induced to the fist R/W coil 3 when the flux of the magnetic recording medium passes through under the first R/W gap 4. On the other hands, for the data track of the high density magnetic disk, the higher rank magnetic head having narrow track width, that is, the second R/W head 9 reads or writes the information on the data track by the same process described above.
As described above, in the conventional complex magnetic head apparatus, one complex head assembled from the first R/W head 5 and the first erase head 13, and another complex head assembled from the second R/W head 9 and the second erase head 17 are separately formed, then the two complex heads are assembled into one slider 1. Accordingly, there arises some problems in that the productivity of the magnetic head is low, the magnetic cross talk is generated by the leakage magnetic flux between the higher rank complex magnetic head and the lower rank complex magnetic head. Also, it easily happens that the relative position drifts of the gaps 4, 8, 11 and 15 of the heads 5, 9, 13 and 17, respectively, and the resultant performance of the head is derated.
Therefore, it is a primary object of the present invention to provide a complex magnetic head and manufacturing method thereof having high performance and superior productivity but no relative magnetic interference between both heads and no relative position drift between the gaps of both heads.
It is another object of the present invention to provide a complex magnetic head having large capacity and high compatibility with lower rank FDDs. The complex magnetic head has a wide-write-narrow-read system which writes signals with a wide head and reads signals with a narrow head.